Jessica Alba signed up for a raunchy bondage-themed advertising campaign in an attempt to encourage young people to vote in the upcoming US Presidential election.

Alba is casted in a dramatic photographic campaign for voter group Declare Yourself, topless with black tape across her mouth and chest and heavy eye make-up.

The pictures include the tag “Only You Can Silence Yourself,” and Jessica, 27, claims they “really resonate” with the issue of voter registration.

She said: “If you don’t register and vote and make a difference, and hopefully change the bad things that are happening in our country, you are essentially just binding and muzzling yourself.

“We sign up for MySpace pages and Facebook pages, and download music off the internet. The least people can do is register to vote online, actually making a difference in their world, not just making their lives a little bit cooler.”

Other stars posing in the campaign include Andre 3000 and Christina Aguilera