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The bitter spat between actor James Franco and his former New York University instructor Jose Angel Santana got a little nastier Tuesday when the ousted professor sued Franco for defamation, calling him "a bully," according to the New York Post.

Santana contends that Franco made "disparaging and inaccurate public statements" about him after he gave the Oscar-nominated actor a "D" for only attending 2 of 14 classes during the spring 2010 semester, according to court documents.

"Whoever was in Clint Eastwood's chair at the Republican National Convention was more present than Mr. Franco was in my classes," Santana told The Post, referring to Eastwood's speech last week at the RNC with an empty chair meant to represent President Obama. "He uses the bully pulpit of his celebrity to punish anyone who doesn't do his bidding."

He taught "Directing the Actor II."

The former professor slapped NYU with a wrongful termination lawsuit in December, blasting the university for isolating him and eventually firing him after he gave Franco a "D." Santana said Franco, 34, was not punished for embarrassing the university publicly and was instead given passing grades by other professors even though he rarely attended classes.

After Santana was fired, Franco, who taught a directing class at NYU last fall, told reporters that he didn't think the class was worth his time.

"I decided to do '127 Hours' instead of going to acting class," he said when asked in April. "I've been in eight years of acting class. I didn't feel like I needed to waste my time with a bad teacher and that I should go and work with [director] Danny Boyle. I felt like that was the right decision."

He was nominated for a Best Actor Oscar for his "127 Hours" role as a hiker trapped in an isolated Utah canyon.

Franco said Santana was fired for being a bad teacher and was only using his name to get attention. NYU has not said why it fired Santana but has denied the claims in his lawsuit, which the school has called "ridiculous" in previous statements.

"He's not going to win the lawsuit and he's not going to get hired at another institution," he said. "It's ridiculous. And I'm teaching at NYU, so what does that say?"

Santana is suing for an unspecified amount in damages, according to the New York Post. His lawyer Matthew Blit did not respond to numerous ABC News requests for comment.

Franco's publicist has not returned a request for comment.