Treasury Secretary Steve Mnuchin formally refused to cough up President Trump’s tax returns to Democrats on the House Ways and Means Committee on Monday.

“I am informing you now that the Department may not lawfully fulfill the Committee’s request,” wrote Mnuchin in a letter sent to the committee’s chair, Rep. Richard Neal (D – Mass.).

“As you recognized, the Committee’s request is unprecedented, and it presents serious constitutional questions, the resolution of which may have lasting consequences for all taxpayers,” added Mnuchin.

The denial comes after officials blew through two deadlines to surrender six years’ worth of Trump’s taxes, first formally requested last month by the committee.

Trump — who has repeatedly expressed a willingness to release his returns, but never done so — responded to the request by pointing Democrats to his lawyers.