“I am informing you now that the Department may not lawfully fulfill the Committee’s request,” Mnuchin wrote in his one-page letter, written in consultation with lawyers from the Department of Justice.

Mnuchin added that the Department of Justice would issue a formal legal opinion.

The denial comes after two missed deadlines by the Treasury secretary, who has previously called the request by House Ways and Means Chairman Richard Neal under an obscure statute of tax law “unprecedented,” arguing it raised “serious constitutional issues” that could have dire consequences for taxpayer privacy.

Neal said in a statement Monday that he was still determining next steps.