President Trump told his accountant to ignore a subpoena from House Oversight Committee Chair Rep. Elijah Cummings (D-MD) in a Monday letter, arguing the request is not “valid or enforceable.”

In the letter, Trump personal attorneys William Consovoy and Stefan Passantino also wrote that the firm is “on notice” regarding the request and signaled that they could take legal action to shield Trump’s financial information.

“We ask that Mazars provide us with at least 10-days notice so that we may take appropriate legal steps to protect our clients’ rights,” Trump’s attorneys wrote in the letter, addressed to Mazars USA outside counsel Jerry Bernstein.

The letter, first reported by Politico, follows a memorandum that Cummings circulated on Friday to lawmakers, saying that he intended to issue a subpoena to Mazars. Cummings seeks personal financial information that Mazars prepared on behalf of Trump and a number of his companies as part of an effort to investigate claims made by Michael Cohen that the President would inflate or deflate the value of his assets to gain tax and other business advantages.

Trump argued in the April 15 letter that Cummings is seeking “confidential information” that is only accessible by the same tax code provision under which the House Ways and Means Committee is demanding the President’s tax returns.

“It is no secret that the Democrat Party has decided to use its new House majority to launch a flood of investigations into the president’s personal affairs in hopes of using anything they can find to damage him politically,” the letter from Trump’s personal lawyers reads.

The letter adds that House Oversight is not a “miniature Department of Justice.”

In a separate release, House Oversight Republicans Jim Jordan (R-OH) and Mark Meadows (R-NC) called the subpoena “unprecedented,” but appear to have stopped short of sending a separate letter to Mazars itself.

In a memo to lawmakers on Monday announcing the issuance of the subpoena, Cummings hit back at Jordan’s statements.

“The Ranking Member is embarking on an unprecedented path of partisanship that all Members of the House of Representatives should find concerning because it could have a detrimental impact on Congress’ ability to exercise its core Constitutional oversight responsibilities for years to come,” Cummings wrote.

Consovoy also represents Trump in his personal capacity in a lawsuit brought by the D.C. and Maryland attorneys general alleging violations of the Emoluments clause, and has written to the Treasury Department to urge it to ignore House Ways and Means’s request for Trump’s tax returns.