“This case involves congressional subpoenas that have no legitimate or lawful purpose,” the suit alleges. “The subpoenas were issued to harass President Donald J. Trump, to rummage through every aspect of his personal finances, his businesses and the private information of the president and his family, and to ferret about for any material that might be used to cause him political damage. No grounds exist to establish any purpose other than a political one.”

The House’s Intelligence and Financial Services Committees issued subpoenas to Deutsche Bank, a longtime lender to Mr. Trump’s real estate company, and other financial institutions two weeks ago, seeking a long list of documents and other materials related to Deutsche Bank’s history of lending and providing accounts to Mr. Trump and his family. People with knowledge of the investigation said it related to possible money laundering by people in Russia and Eastern Europe.