Ex-New York Mayor Rudy Giuliani is refusing to appear before the U.S. House of Representatives committee investigating the Jan. 6, 2021, Capitol attack unless he is allowed to record the proceedings, a spokesman for the panel said on Thursday.

Giuliani, who served as former U.S. President Donald Trump's attorney, had previously agreed to a "transcribed interview" with the committee before making the demand, spokesman Tim Mulvey said.

"Mr. Giuliani is an important witness to the conspiracy to overthrow the government and he remains under subpoena," Mulvey said. "If he refuses to comply the committee will consider all enforcement options."

An attorney for Giuliani could not immediately be reached for comment on Thursday evening.

The former mayor tweeted a story on The Gateway Pundit website reporting that he had asked for live national television coverage of his scheduled testimony, a request that had been denied by the committee.

The committee is trying to establish Trump's actions while thousands of his supporters stormed the Capitol in January last year, sending members of Congress and then-Vice President Mike Pence rushing to take cover.

Congress had been meeting to formally certify Democrat Joe Biden's victory over Republican Trump in the November 2020 presidential election.

More than 900 people, including many Trump White House aides, have been interviewed in the committee's investigation.

(Reporting by Patricia Zengerle and Dan Whitcomb; Editing by Kenneth Maxwell)