don't hold back lou...

Sienna Miller, Hayden Christensen and Guy Pearce just started filming "­Factory Girl," in which Miller plays Andy Warhol's drug-addled muse Edie Sedgwick.

But Lou Reed has already formed his opinion of director George Hickenlooper and his cast.

"They're all a bunch of whores," the rock god tells us.

"I read that script," Reed said the other night at a party for his new photo shows at the Hermès boutique and the Steven Kasher Gallery. "It's one of the most disgusting, foul things I've seen — by any illiterate retard — in a long time. There's no limit to how low some people will go to write something to make money."