Sean Penn has quit his job as contributing reporter for the San Francisco Chronicle, after the newspaper dubbed Venezuelan president Hugo Chavez a "dictator."

The politically charged star has carried out a series of assignments for the paper - edited by Sharon Stone’s ex-husband Phil Bronstein - visiting Iraq and Iran as a contributing reporter.

But Penn has severed all ties with the California publication in a stinging letter to Bronstein, which has was published in Thursday’s (17Jan08) edition.

Penn writes, "I could only hope this great city was more clever than its increasingly lamebrain paper. Chavez was democratically elected.

"In the paper’s attack on Oliver Stone, who, agree with him or not, has at least the balls, passion and intellectual curiosity to pursue information away from a porcelain dumping bowl and a desperate newspaper, we see another attempt to marginalize the outspoken." Penn signed the letter "former SF Chronicle contributing reporter."

Bronstein has responded, writing alongside Penn’s piece, "He’s a great actor and a great director. People get riled up about a lot of things. Particularly in this day and age; they get to express themselves. We were more than happy to print this letter."