Taylor Swift has been cast opposite Zac Efron in 'The Lorax'.

It was announced today (17.03.11) that the 21-year-old singer will join the cast to voice the love interest of the 'High School Musical' actor's character.

Based on a Dr Seuss children's book, the CGI-animated movie will also star Danny Devito, Betty White, Ed Helms and Rob Riggle.

The film follows Ted, voiced by Zac, who seeks out the Lorax, played by Danny, in a tale which contains a message about the importance of preserving the environment.

Taylor will voice Audrey, the girl of Ted's dreams, cementing her status as an actress after her appearance in 'Valentine's Day' last year.

Chris Renaud is directing the picture which is being made by studios Universal Pictures and Illumination Entertainment and will be released in March 2012.

One person certain to watch the film is Taylor's dad, with the beauty admitting last year that he is her biggest fan.

She said: "My dad is adorably optimistic, positive, pie-in-the-sky. He thinks every new song I write is my best. He sells T-shirts at my merchandise stands and hands out guitar picks to fans."