The Milk star sparked controversy this week (beg13Feb12) when he accused the British government of "ridiculous colonialism" over its ownership of the archipelago in the Atlantic Ocean.
But Weston, who was among British troops who saw off an invasion of the Falklands by Argentinian forces in 1982, has hit back at the Hollywood star, insisting his comments are idiotic.
Welshman Weston, who suffered horrific burns when the naval ship he was on was bombed and set on fire, tells The Sun, "People give too much credence to actors. Sean Penn is living, breathing proof that just because you are famous doesn't mean you know what you are talking about.
"Penn is an idiot. It's bad for people to think you're a fool. You don't need to open your mouth to prove it. By opening his mouth on this, Sean Penn proves he is a fool."
Weston provided one of the lasting images of the Falklands War when he went public with his severe injuries on a TV show.