"The legal implications of this request could affect protections for all Americans against politically-motivated disclosures of personal tax information, regardless of which party is in power", Mnuchin wrote.
Trump nearly immediately said he opposed the request, and one of his lawyers, William Consovoy, on Friday asked the Treasury Department and IRS to withhold the returns until the Justice Department issues an opinion on whether the request is legal.
In the latest contest between Democrats and the administration, Treasury Secretary Steve Mnuchin told Rep. Maxine Waters that he wouldn't come back to Congress if forced to stay past 5:15pm. Neal asked for Trump's returns a week ago.
Mnuchin, speaking on CNBC television, said that a call with Chinese Vice Premier Liu He on Tuesday night was productive and discussions would be resumed on Thursday.
Trump broke with 40 years of presidential campaign tradition by declining to release his personal returns before the 2016 election.
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Once you've moved on in the way that Lambert has supposedly moved on, you don't need to throw shade at your ex like that. If she could go back and do it again, she'd follow the same trajectory, choosing her artistry over people-pleasing.
In the days leading up to Wednesday's response, both Mnuchin and IRS Commissioner Chuck Rettig gave nonspecific accounts during testimony before the House and the Senate about who would reply to Neal. No law prevents a taxpayer from releasing returns that are under audit.
"It is our intent to follow the law and that is in the process of being reviewed, " Mnuchin told a House Appropriations subcommittee with responsibility for his budget.
Mnuchin thought he could outsmart Waters, by getting testy, trying to play a mind game and then having the audacity to tell the senior top Democrat how to do her job and when to bang her gavel.
He did not explain who exactly he was referring to, but he said this list could include Democrats in Congress and their financial supporters outside Washington.
Rettig said he hadn't been instructed not to comply with the request by anyone acting on the White House's behalf. Those attachments would contain more information, though still not as much as a release of Trump's full federal tax return.
"Unfortunately", she said, "we are all pressed for time". "That's where the real action is - in those federal forms - but even then, they are going to be probably a little too summary to answer some of the questions".
"The requests for [Trump's] private tax information are not consistent with governing law, do not advance any proper legislative objective, and threaten to interfere with the ordinary conduct of audits", said William S. Consovoy, Trump's attorney, in a statement.