Paris Hilton has slammed reports she has undergone plastic surgery to enhance the size of her breasts.

The hotel heiress - who once flaunted her petite A-cups on the cover of U.S. magazine Vanity Fair - sparked rumours she has had breast implants after she was recently photographed with a noticeably larger chest.

But a spokesperson for Hilton insists she hasn't had her breasts surgically altered, crediting "a prototype from her Paris Hilton 'push-up' bra line" for the star's enlarged cleavage.

The representative adds: "Paris has never had plastic surgery."