Penn explains Team America letter

Oscar winner Sean Penn has defended his decision to write a letter to film- makers Matt Stone and Trey Parker, objecting to their satirical puppet movie Team America: World Police.

The Mystic River star became enraged when the pair - also responsible for animated TV series South Park - jokingly encouraged Americans not to vote.

Penn then fired off his letter, which he ended with the words "f**k off".

The 44-year-old actor's anti-war views are parodied in the film, but Penn claims not to be bothered by this.

He explains: "I just saw a guy who told people not to vote and I thought it was stupid."

Stone and Parker have previously expressed their satisfaction at the publicity Penn's outburst afforded their movie.