Jessica Alba is encouraging Americans to vote by posing topless – save for some strategically applied black tape – for a bondage-inspired billboard advert.

The actress appears heavily made up and with tape across her breasts and mouth in the ad, paid for by voter group Declare Yourself.

Jess explains the thinking behind the provocative campaign as: "If you don't register and vote, you are muzzling yourself."

The actress adds, "I think it is important for young people to be aware of the need we have in this country to get them more active politically.

“People respond to things that are shocking.”

Jess was the unwitting participant in another 'shocking' photo this week – click here to see the actress being upstaged by Julianna Margulies' nether regions.