March 13 (Reuters) - A federal judge on Friday blocked subpoenas issued by the U.S. Justice Department as part of its criminal investigation into Federal Reserve Chair Jerome Powell's handling of renovations of historic buildings used by the central bank.

U.S. Attorney for the District of Columbia Jeanine Pirro, whose office is spearheading the investigation, promised to appeal Chief U.S. District Judge James Boasberg's decision. Powell, a frequent target of Donald Trump's ire, has called the investigation a pretext for the Republican president to gain more influence over the Fed and monetary policy.

Powell on January 11 disclosed the Justice Department's probe concerning a project to renovate historic buildings at the Fed headquarters in Washington. The Fed's Board of Governors made a motion to quash the subpoenas, which sought information about the renovations and Powell's July 2025 testimony before the Senate Banking Committee.

Powell has described the probe as a threat to Fed independence and part of Trump's attempts to pressure the Fed to cut rates.

The judge agreed, saying a "mountain of evidence" suggests the investigation was to pressure the Fed chair to lower rates or resign. 

"The Government has produced essentially zero evidence to suspect Chair Powell of a crime; indeed, its justifications are so thin and unsubstantiated that the Court can only conclude that they are pretextual," Boasberg wrote.

Pirro, a Trump appointee, said the judge "has neutered the grand jury's ability to investigate crime; as a result Jerome Powell today is now bathed in immunity" and told reporters that her suspicion that a law was violated is enough reason to pursue cases.

Republican Senator Thom Tillis has vowed to use his spot on the Senate Banking Committee to block any Fed nominee while the probe stays open, effectively freezing the confirmation of Trump's pick to succeed Powell as Fed chair when his leadership term ends in mid-May.