Former Lehman Brothers Holdings Inc. Chairman and Chief Executive Richard S. Fuld Jr. plans to tell lawmakers Tuesday that regulators knew everything that was going on inside Lehman "in real time" as it neared bankruptcy, an allegation that will pit him against others testifying with him in Washington.

Tuesday's showdown with the House Committee on Financial Services will mark the first time Mr. Fuld has spoken publicly since a bankruptcy examiner released a stunning report on Lehman's collapse that raised the specter that...