As the conservative economist came under questioning before the Senate Banking Committee, she was sharply criticized by Alabama Democrat Doug Jones for once describing a man who managed to get more than $60 million of his bogus currency - "Liberty Dollars" - into circulation as "the Rosa Parks of monetary policy."

"Rosa Parks, in one act of courage, defied the Jim Crow laws and tried to bring down the walls of oppression that kept a race of people from voting and from basic human and civil rights," Jones said.

"Senator Jones, the last thing that I would ever do is demean the courage of Rosa Parks," Shelton responded.

"Well you did. You realize that don't you?" Jones fired back.

"I apologize, I apologize for the comparison, I truly do," Shelton said. "The gentleman you are referring to, he did an audacious thing."

Shelton's exchange with Jones was well out of the ordinary for a hearing to consider her nomination for a position largely focused on the vagaries of interest rate policy and how that supports the U.S. economy.

Shelton, nominated by President Donald Trump for one of two vacant seats on the Fed's board, has in the past written favorably about a return to the gold standard, under which the value of the dollar would be pegged to the precious metal.

The United States abandoned the gold standard in 1971, but a number of critics have continued to advocate for a currency backed by it or somehow linked to other commodities.

One gold devotee - Bernard von NotHaus - was convicted in 2011 of circulating his U.S. currency lookalikes and was later sentenced to six months of house arrest. Shelton's "Rosa Parks" remark was recorded in a 2012 You Tube video (https://www.youtube.com/watch?v=hdlZi2KPXhU&t=46m00s) about a year after NotHaus' conviction.

"I've called him the Rosa Parks of monetary policy because he is challenging, challenging what the federal government has done with regard to carrying out its constitutional responsibility to maintain the value of U.S. money," she said in the video, one of a series she made for the Atlas Network as director of the free-market group's "Sound Money Project."

(Reporting by Ann Saphir; Writing by Dan Burns; Editing by Andrea Ricci)