Activist investor Carl Icahn said the directors of Lions Gate Entertainment failed shareholders this week after the film studio rejected his $575 million buyout offer.

In a letter to CEO Jon Feltheimer, released Wednesday, Icahn said Lions Gate has rewarded executives with "bonuses, options and golden parachutes" as the value of the company's stock declined.

"If the stock price of a company remains stagnant for years, as it has with Lions Gate, then clearly something is wrong," Icahn wrote. "I suggest that your directors have failed shareholders."

The company's shares, which traded just below $12 around this time in 2007, trade for around half that today.

The studio's board rejected Ican's offer unanimously, according to a regulatory filing Tuesday.

Lions Gate rejected an identical offer of $6 per share from Icahn last month that would have raised his stake in the company to 30 percent, from 19 percent.

The company also rewrote its bylaws to make a takeover attempt more difficult, a move Icahn has said he will challenge in court.

A representative for Lions Gate could not immediately be reached for comment Wednesday morning.

Shares of Lions Gate Entertainment Inc. rose 9 cents, or 1.5 percent, to $6.08 in morning trading.