(Bloomberg) -- Senator Elizabeth Warren said revelations about investment transactions last year by Federal Reserve officials raised questions about Jerome Powell’s leadership of the U.S. central bank.

“For Fed officials to actively trade in the market raises legitimate questions about conflicts of interest and insider trading,” the Massachusetts Democrat said Tuesday during a Senate speech. “These Fed officials actually show, at a minimum, really bad judgment,” she said, adding it’s “not clear why Mr. Powell did not take steps to prevent these activities.”

The Fed is under fire following revelations about unusual trading activity by some senior officials last year as the central bank fought to shelter the U.S. economy from Covid-19.

Warren, who has publicly opposed Powell’s renomination as Fed chief when his term expires in February, said he had “failed as a leader.”

She called Monday for the Securities Exchange Commission to investigate whether the transactions violated insider trading rules, citing an Oct. 1 Bloomberg News report about trading by Vice Chair Richard Clarida in his 2020 financial disclosures.

Separately, two regional Fed presidents recently announced their departures after revelations about their trading activity last year. 

Powell, who is waiting to learn if President Joe Biden will nominate him for a second term, had already opened an internal examination of the central bank’s ethics rules. The Fed said Monday that Powell has asked its inspector general to conduct a review of the trades to make sure they were in compliance with Fed rules and the law.

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