A federal lawsuit from an ex-employee at the Miami and Atlanta offices of commercial real estate giant Jones Lang LaSalle Americas Inc. alleges she was fired for blowing the whistle about apparent widespread tax and securities laws violations.

The lawsuit—filed Wednesday in the Northern District of Illinois—claims to unveil a widespread practice of creating "holdback accounts" that were often used improperly for personal expenses, such as first-class plane tickets, luxury hotel rooms and ski trips, by executives in Atlanta, Nashville, Chicago and New York.