Hugh Hefner has vowed to carry on having sex until he's 100.

The 81-year-old Playboy magazine founder, who has three live-in lovers, will still be up for bedroom action even when he reaches the landmark age.

He said: "I'll keep having sex until I'm 100. I have three girlfriends, a TV show and a hugely popular men's magazine."

Hugh lives in the Playboy mansion with girlfriends Holly Madison, Kendra Wilkinson and Bridget Marquardt but revealed he is ready to commit himself to Holly.

He said: "I do eventually think Holly and I will have a monogamous relationship.

"Do Kendra and Bridget know that? Sure it's fine with them, they are here for very different reasons."

Kendra recently revealed Hugh can no longer satisfy her sexually.