The NASD charged

Oppenheimer & Co.

(OPY) - Get Report

with failing to cooperate in a regulatory investigation into municipal bond trades at the brokerage.

In a civil complaint, the securities industry's largest self-regulatory organization also charged Oppenheimer with failing to turn over trading information and retaining email communications between its employees.

The brokerage is disapointed in the NASD's action, said Marvin Pickholz, an attorney for Oppenheimer.

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"The firm respects and takes seriously the NASD's regulatory function and investigative process," Pickholz said. "The firm has made and continues to make every effort to cooperate with the NASD and all other regulators. The firm believes that it cooperated fully with the NASD in its investigation."

The investigation focuses on allegations that Oppenheimer failed to report certain municipal bond trades, while other transactions were reported late or inaccurately. Oppenheimer is not associated with the mutual fund firm

Oppenheimer Funds

.

"Oppenheimer's failure to fully and accurately report municipal bond transactions deprived the investing public and market participants of critical information,'' said NASD Vice Chairman Mary Schapiro. "And all firms have a fundamental obligation to cooperate fully with NASD in its investigations."

A hearing on the charges is pending. The company couldn't immediately be reached for comment.