The spat between Babel director Alejandro González Iñárritu and screenwriter Guillermo Arriaga has escalated into a public row over which of them deserves credit for the film's ideas.

Babel is the third - and presumably the last - collaboration between the two Mexicans, who previously worked together on Amores Perrosand 21 Grams.

Iñárritu sent an open letter to Mexican magazine Chilango, accusing Arriaga of having an "unjustified obsession with claiming the sole authorship" of the film. The 12 signatories to the letter included Babel cast members Gael García Bernal and Adriana Barraza, and its Oscar-winning composer, Gustavo Santaolalla. Arriaga responded in a radio interview that his earlier complaints were intended to defend his rights as a screenwriter. "Alejandro never says 'our trilogy'," Arriaga wrotes. "He says, 'my trilogy'."