Cameron Diaz believes the perfect breast should be able to fit inside a "champagne glass".

The actress is glad she has a modest but "pert" chest because her mother told her that very large breasts are not the best.

In an interview with German magazine TV Movie, she said: "I have to admit that I like my breast to be firm and pert. My mother always told me that the perfect breast fits into a champagne glass. I found that cool and was happy that my breast stayed small."

Although she is content with her cleavage now, Cameron admits when she was younger she envied the massive chest of her grandmother

She added: "Back in the day I always wanted the giant breasts of my grandma ... Many women think you need large breasts, but I'm the living proof that you can go far with small ones."

However, Cameron would not rule out ever having a boob job - which is the ambition of her character Elizabeth Halsey in new comedy movie 'Bad Teacher' - if she felt her breasts needed a boost.

Speaking about whether she'd ever go under The Knife to improve her assets, she said: "So far I'm quite happy with what I have. It's not that much but I have some really effective push up bras. But I would never say never, of course. Maybe one day, if I don't like them anymore."