WASHINGTON - Former U.S. President Donald Trump filed a lawsuit on Friday seeking to avoid being compelled to testify or provide any documentation to a congressional panel investigating his supporters' violent attack on the U.S. Capitol last year.

The House committee investigating the attack of Jan. 6, 2021 had unanimously issued a subpoena for the Republican former president to appear on or about Nov. 14.

Lawmakers had also extended through this week their initial Nov. 4 deadline for Trump to turn over any related documentation.

Representatives for the panel could not be immediately reached for comment on the lawsuit filed in the U.S. District Court for the southern district of Florida in West Palm Beach.

The subpoena infringes Trump's constitutional right to free speech, his lawyers said in the 41-page filing that called the investigation a "quasi-criminal inquest," and adding that the panel lacked the authority to compel testimony.

They also said the panel had not responded to Trump's alternative offer to respond in writing to specific questions. In a Nov. 9 letter to the panel attached to the lawsuit, Trump's attorneys said he would "consider" whether providing written responses "would be appropriate."

The letter said Trump "voluntarily directed a reasonable search for documents in his possession" but it "found no documents responsive to this request."

The committee has held a series of hearings as it seeks to make its case to the public that Trump was largely responsible for the deadly assault on Congress while lawmakers met to formally declare his loss to Democrat Joe Biden.

The panel has not said how it will proceed if Trump disregards the subpoena request.

The committee, set to dissolve when the current Congress ends, could be reconstituted in some form depending on which party controls the House when its next term starts in January, an outcome hingeing on the vote count in Tuesday's midterm election.

(Reporting by Susan Heavey; Editing by Clarence Fernandez)