The U.S. Securities and Exchange Commission sued former ConvergEx Group executive Khaled "Kal" Bassily, accusing him of fraudulently reaping millions of dollars for his onetime employer and himself by charging hidden markups on customers' securities trades.

In a complaint filed on Tuesday in federal court in Manhattan, the SEC said Bassily, 50, routinely misled customers, including charities, religious organizations and retirement funds, about their trading costs.

Bassily, a Manhattan resident with a business degree from Columbia University, also coached traders on the amount of hidden charges, known internally as "trading profits," they could collect without customers noticing, the complaint said.

The SEC said the scheme ran from October 2006 until December 2011, and "directly enriched" Bassily by enabling him to collect millions of dollars of bonuses.

Bassily had been head of the global transition management unit of ConvergEx Execution Solutions LLC prior to being fired in September 2013.

ConvergEx agreed three months later to pay more than $150 million to settle U.S. criminal and civil probes into alleged customer overcharges, and various units admitted wrongdoing.

The privately held company is based in Manhattan, and provides brokerage and trading-related services for institutional investors.

Jim Benjamin, a lawyer for Bassily, said in a statement: "Mr. Bassily acted in good faith by following ConvergEx's approved business model. He will vigorously defend himself against these charges, and looks forward to his day in court."

According to Financial Industry Regulatory Authority records, Bassily was fired because of concerns over "certain communications with clients" and transactions prior to 2012.

The SEC lawsuit against Bassily seeks to recoup ill-gotten profits, impose civil fines, and obtain other relief.