NEW YORK -- Mentor Graphics and billionaire Carl Icahn are back it, squabbling over whether the notorious investor's handpicked representatives should have been nominated for the software company's board.

Icahn made headlines last year when he attempted to shake up the company directors in the hopes of driving up the stock price. After a protracted battle, he succeeded in landing three nominees on the EDA software developer's board.

But Mentor bid its time, then struck back, failing to re-nominate two of Icahn's chosen representatives for its current fiscal year. Instead, the company chose Keith Barnes, a former software executive with Verigy and Cadence, and Daniel McCranie, chairman of ON Semiconductor.

Today, Icahn issued an open letter chastising company leaders for their actions, and accusing the company of being underhanded. "As the company's largest shareholder, we are disappointed by the Board's decision not to re-nominate Gary Meyers and Jose Maria Alapont, two of the three directors elected by shareholders as a result of our proxy contest last year. We view this action as an affront to shareholders and shareholder democracy – especially given that ISS recommended last year that shareholders vote FOR both Messrs. Alapont and Meyers.

"This action, in combination with the board's recent decision to extend the company's poison pill without shareholder approval – a practice frowned upon under the ISS proxy voting guidelines – clearly indicates that the company's long track record of poor corporate governance has still not changed. Apparently, our three nominees, as a minority on a board with a still-entrenched majority, were unable to prevent this contemptuous behavior.

"While it is past the deadline for nominating directors at this year's annual meeting, we wanted to inform you and the rest of the company's shareholders that these actions have not gone unnoticed."

Icahn is Mentor's largest shareholder, owning 14.67% of the company as of Dec. 31.

Mentor, which ranks among the top semiconductor and printed circuit board software design companies in the world, has not commented on Icahn's letter.