"Due to the serious constitutional questions raised by this request and the serious consequences that a resolution of those questions could have for taxpayer privacy," Mnuchin wrote in a letter, he expects to give Congress "a final decision by 6 May, after receiving the Justice Department's legal conclusions," according to WHIO radio station report.
Mnuchin, who labeled the Democrats' request for Trump's tax returns "unprecedented," ignored the Tuesday 5 p.m. deadline set by the lawmakers.
READ MORE: Mnuchin Tells US Lawmakers Time Needed to Provide Trump's Tax Returns — Reports
According to WHIO, Mnuchin's 10-page letter "certainly gives off the feeling that Mnuchin is in no mood" to provide Trump's tax returns to the Democrats. The letter section titled "Constitutional limits" states that "Congress's investigative power is not unlimited."
"Article I grants Congress no express power to investigate," Mnuchin wrote, referring to Article I of US Constitution which grants Congress various powers.
House Democrats have a number of ways to respond to the treasury secretary's letter, the Washington Post writes. Possible responses include sending a final written warning, issuing a subpoena for the tax records under a 1942 law "that appears to give [the lawmakers] access to virtually any tax return," or summoning top administration officials to the Capitol to testify.
Trump, who appears to be unwilling to release his tax records, claims he is currently under audit and will not release tax returns until the audit is complete.
"I'm always under audit, it seems, but I've been under audit for many years because the numbers are big, and I guess when you have a name, you're audited", Trump said, commenting about Neal's request.