Mexican directors Alfonso Cuaron and Guillermo del Toro and Jorge Vergara, producer of Cuaron's Y Tu Mama Tambien and del Toro's The Devil's Backbone, have declined to submit their films to the prestigious Mexican Ariel Awards, in protest at the "lack of transparency" in the voting process.

"We hope that our non-participation will initiate some changes in the [Mexican Academy of Cinematographic Arts & Sciences] which is badly in need of new blood," Vergara said. The Ariel Awards are Mexico's equivalent of the Oscars. The Academy has not responded to their actions.

Cuaron and Vergara have also been angered by the Academy's decision to select Maryse Sistach's Perfume De Violetas instead of Y Tu Mama Tambien as Mexico's Best Foreign Oscar entry.

Although they don't dispute the quality of Sistach's drama, they point out that it does not have the profile of Y Tu Mama Tambien, which was released this week in the US by IFC Films, the theatrical distribution arm of the Independent Film Channel.

Last year, Cuaron and Vergara demanded an overhaul of the ratings system in Mexico when Y Tu Mama Tambien was given a 'C' rating, restricting it to local audiences aged 18 and above. Although commercially limiting, the 'C' certificate did not stop the raunchy comedy - about two teenage boys who embark on a sexual road-trip with an older woman - from breaking box office records on its opening week in Mexico.

Vergara and Cuaron, partners in their new production company Anhelo, demanded to know the criteria by which the Direccion de Radio Television y Cinematografia (RTC) decided on the C rating. The controversy provoked much debate about Mexico's antiquated ratings system, but so far no changes have been made.