Former Treasury Secretary Janet Yellen criticized the Trump administration's Department of Justice investigation into Federal Reserve Chairman Jerome Powell, calling it a "disturbing" attack on the central bank's independence.

Yellen, who previously served as Federal Reserve chair before Powell, described the investigation as "unprecedented" and "the most recent and most disturbing" development in what she characterized as efforts to undermine the Fed's autonomy.

The investigation represents a rare instance of the Justice Department examining the actions of a sitting Federal Reserve chair. The Federal Reserve operates as an independent agency designed to make monetary policy decisions without political interference.

Powell has served as Fed chair since 2018, when he was appointed by former President Trump. The central bank's independence has been a cornerstone of U.S. monetary policy for decades, allowing it to make decisions based on economic data rather than political considerations.

Yellen's comments highlight ongoing tensions between political leaders and Federal Reserve officials over the central bank's role in economic policy. The Fed chair position requires Senate confirmation but is intended to operate independently once confirmed.