President Donald Trump, backed by Michael Best & Friedrich and Consovoy McCarthy Park, is going on the offensive to block a U.S. House Oversight Committee subpoena targeting the president's accountant.

The complaint, filed in U.S. District Court for the District of Columbia on Monday, looks to head off a subpoena filed by U.S. Rep. Elijah Cummings, the chairman of the House Oversight Committee, which seeks financial statements, documents and communications from the president's longtime accounting firm, Mazars USA LLP.

The lawsuit marks the first time Trump has taken the House's Democratic majority to court in a bid to block enforcement of a congressional subpoena. The litigation comes as House lawmakers have demanded, separately, copies of Trump's tax returns. U.S. Treasury officials have yet to produce those records. The deadline is Tuesday.

“There is no possible legislation at the end of this tunnel; indeed, the Chairman does not claim otherwise,” according to the lawsuit. “With this subpoena, the Oversight Committee is instead assuming the powers of the Department of Justice, investigating (dubious and partisan) allegations of illegal conduct by private individuals outside of government. Its goal is to expose Plaintiffs' private financial information for the sake of exposure, with the hope that it will turn up something that Democrats can use as a political tool against the President now and in the 2020 election.”

The lawsuit seeks declaratory judgment that Cummings' subpoena is unenforceable. It also seeks a temporary restraining order and preliminary injunction prohibiting Mazars from producing the requested information.

Stefan Passantino of Michael Best & Friedrich represents the Trump Organization in the lawsuit. Passantino also represents other financial entities owned by Trump, including the Old Post Office LLC. Passantino, who led Dentons political law group before joining the Trump White House as deputy White House counsel, joined Michael Best in September.

Trump is represented by a team from Consovoy McCarthy Park, which includes law firm partners William Consovoy and Patrick Strawbridge, and associate Cameron Norris, a former clerk for Justice Clarence Thomas.

Consovoy and Strawbridge, who also clerked for Thomas, also represent Students for Fair Admissions in a lawsuit against Harvard for allegedly discriminating against Asian-Americans by setting a higher admissions bar for them.

Consovoy is also involved in a lawsuit seeking to undo mandatory bar fees in Texas. It is one of at least four lawsuits nationally challenging mandatory bar membership in the wake of two U.S. Supreme Court decisions last year impacting states' ability to require union or professional dues as a condition of employment.

Trump's lawsuit is posted below: