In response to the suit, Trump attorney Jay Sekulow told Politico, "We will respond to this latest effort at presidential harassment in court.
In the lawsuit, committee attorneys noted that the panel has no obligation to explain the reasons for which it's seeking Trump's tax returns, however, they added, "the Committee's need for the materials requested here is evident."
Among other things, the committee says it's investigating whether Trump is complying with tax laws and the administration of tax laws and policies related to presidential tax returns.
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"Indeed, President Trump himself has repeatedly questioned the integrity of the process by which the IRS audits his tax returns, complaining that his returns are under 'continuous audit' and that the IRS's policy of annually auditing Presidential returns is 'extremely unfair,'" attorneys wrote in the lawsuit. "The President has also publicly theorized that the IRS audits him because of his assertedly strong Christian faith."
The attorneys wrote that by refusing to provide the panel with Trump's tax returns, officials had "mounted an extraordinary attack on the authority of Congress to obtain information needed to conduct oversight of Treasury, the IRS and the tax laws on behalf of the American people."
They alleged officials denied previous requests and defied subpoenas from the committee "in order to shield President Trump's tax return information from Congressional scrutiny."
In a letter sent May 6 to Neal, Mnuchin wrote that a request for Trump's tax returns made by the House Ways and Means Committee's lacked "a legitimate legislative purpose," as required by Supreme Court precedence, The Associated Press reported. He said his decision to deny access to the returns was made on the advice of the Department of Justice.
Mnuchin has previously told Congress that authorities "will comply with the law" in regard to releasing Trump's tax returns. He also said Neal's request could weaponize private tax returns for political purposes, according to the AP.
Trump has repeatedly declined to release his tax returns, citing an ongoing audit.
“I would love to give them, but I’m not going to do it while I’m under audit,” Trump told reporters April 10.