Justice Department backs Steven Mnuchin in fight for Trump's tax returns

• The Office of Legal Counsel agreed with Mnuchin's determination that the House Ways and Means Committee's subpoena did not have a "legitimate legislative purpose."
• "The Committee's asserted purpose—to consider legislation regarding the IRS's practices in auditing presidential tax filings—was implausible," the agency says in the memo.
• In May, the Treasury secretary defied a subpoena from the committee by not authorizing the IRS to give Trump's personal and business tax returns to congress.

Steven Mnuchin, Secretary of the Treasury of the United States of America, during a G-20 meeting on June 08, 2019 in Fukuoka, Japan.

Florian Gaertner | Photothek | Getty Images

The Justice Department on Friday supported Treasury Secretary Steven Mnuchin's argument against turning over President Donald Trump's tax returns.

In an opinion signed by Steven Engel, assistant attorney general for the Office of Legal Counsel, the agency agreed with Mnuchin's determination that the House Ways and Means Committee's subpoena did not have a "legitimate legislative purpose."

"The Committee's asserted purpose—to consider legislation regarding the IRS's practices in auditing presidential tax filings—was implausible," Engel wrote in the memo.

The opinion comes after Mnuchin defied a subpoena from the committee by not authorizing the IRS to give Trump's personal and business tax returns to congress.

House Democrats issued subpoenas to Mnuchin and IRS Commissioner Charles Rettig last month seeking the documents.

A spokesperson for the House Ways and Means Committee had no immediate comment when reached by CNBC. The DOJ and the Treasury Department did not immediately respond to requests for comment.

The memo was first reported by the Wall Street Journal.