Ashley Greene is urging high school girls to donate their unwanted prom dresses to those who can't afford their own.

The 'Twilight' actress has become the official spokesperson for - an organisation that ensures all teenage girls get their dream prom night - for the third year in a row and recalled saving up to buy her own gown.

In a statement the 24-year-old star said: "In high school, I had to work several jobs to save enough to buy a prom dress.

"It was so worth it: I had a blast at prom! Every girl should have the chance to have that experience."

Ashley - who recently split up with Joe Jonas and has since been seen with Kings Of Leon bassist Jared Followill - has donated several of her own dresses and next plans to give the white Lela Rose gown she wore to the Chrysalis Butterfly Ball.

Over the past few years Miley Cyrus, Demi Lovato and Taylor Swift have also donated items to the charity.