President Donald Trump moved to fire Federal Reserve Gov. Lisa Cook “effective immediately,” in a letter posted to social media Monday, citing mortgage fraud allegations as his reasoning.

“I have determined that there is sufficient cause to remove you from your position,” Trump wrote. “The American people must be able to have full confidence in the honesty of the members entrusted with setting policy and overseeing the Federal Reserve. In light of your deceitful and potentially criminal conduct in a financial matter, they cannot and I do not have such confidence in your integrity.”

The conduct in question arises from a criminal referral Federal Housing Finance Agency Director Bill Pulte made to the Justice Department this month, alleging Cook obtained two mortgages in 2021, two weeks apart, but claimed in paperwork that each would be used as a primary residence.

“It is inconceivable that you were not aware of your first commitment when making the second. It is impossible that you intended to honor both,” Trump wrote Monday. “At a minimum, the conduct at issue exhibits the sort of gross negligence in financial transactions that calls into question your competence and trustworthiness as a financial regulator.”

Cook, in a statement Monday, said she “will not resign.”

“President Trump purported to fire me ‘for cause’ when no cause exists under the law, and he has no authority to do so,” she said. “I will continue to carry out my duties to help the American economy as I have been doing since 2022.”

The move presumably sets up a legal battle over the extent of presidential powers. The president is permitted to remove a Fed governor for cause, but none has previously done so.

Trump has relentlessly badgered Fed Chair Jerome Powell over his reluctance to lower interest rates and has publicly discussed firing him but has walked back the threat each time.

The Fed did not immediately comment Monday.

Cook’s attorney, Abbe Lowell, in a statement, said Trump’s “demands lack any proper process, basis or legal authority.” 

“President Trump has taken to social media to once again ‘fire by tweet’ and once again his reflex to bully is flawed,” Lowell said. “We will take whatever actions are needed to prevent his attempted illegal action.”