Sienna Miller is being stalked by an obsessed transvestite named Peter, and has been forced to upgrade her home security system and hire two bodyguards to protect her.

The bodyguards were employed for the London premiere of 'Factory Girl' after Sienna received a number of "bizarre" letters.

The scare has led the popular star to lose sleep, and according to Britain's Daily Star newspaper: "Sienna has been bombarded with bizarre letters from a transvestite and has hired two security men. In his letters he talks about being obsessed with her look. He tries to follow her everywhere.

"The poor girl hasn't been sleeping properly because she has been so scared. Things just got to the point that she just had to take extra care of herself."

'Peter' is allegedly a transvestite who has fetishes for women's wigs, stilettos and fur coats.

He is also said to be obsessed with the 'Factory Girl' movie, which stars Sienna as Edie Segdwick, pop artist Andy Warhol's muse.

Photo: Getty Images