NEW YORK (Reuters) – Goldman Sachs Group Inc (GS.N) was sued on Thursday by a former managing director who said the Wall Street bank retaliated against him and fired him after he complained about its dealings with an unidentified, “notorious European businessman.”

Christopher Rollins, now chief executive of BTIG Ltd, a London-based unit of investment banking and trading firm BTIG LLC, is seeking at least $50 million plus punitive damages in his complaint filed with the U.S. District Court in Manhattan.

The 2000 Harvard University graduate accused Goldman and Jim Esposito, promoted this week to global co-head of its trading business, of violating his rights as a whistleblower under the federal Dodd-Frank law, and also accused Goldman of defamation.

“The suit is without merit and we intend to vigorously contest it,” Goldman spokesman Michael DuVally said in an email, responding to a request for comment on behalf of…