The SEC has charged Leon Cooperman and Omega Advisors with insider trading in a six-year-old case involving shares of Atlas Pipeline Partners.

The stock market watchdog said Cooperman, 73, bought into Atlas Pipeline Partners before it struck a deal in 2010 to sell its Elk City facilities.

Cooperman, who was already one of Atlas’ largest shareholders at the time, allegedly used confidential information provided by an unnamed Atlas executive, and profited as Atlas shares rose 30%.

"We allege that hedge fund manager Cooperman, who as a large APL shareholder obtained access to confidential corporate information, abused that access by trading on this information," said Andrew J. Ceresney, director of the SEC's Division of Enforcement. "By doing so, he allegedly undermined the public confidence in the securities markets and took advantage of other investors who did not have this information."

According to CNBC, the former Goldman Sachs executive and Omega Advisors said they rejected a settlement offer from SEC and were ready to fight the charges.

"We will vigorously defend ourselves," he said in a statement to the television channel, and called the SEC charges "without merit."

The SEC has also accused Cooperman of contacting the unnamed executive and trying “to fabricate a story" in the event both were questioned about the trades.

Cooperman established Omega Advisors in 1991 after a 25-year career at Goldman Sachs, signing off when he was a general partner of Goldman Sachs & Co. and chairman and chief executive officer of Goldman Sachs Asset Management.