Director/producer Kevin Allen has obtained the movie rights to the 1954 work, which features the dreams and innermost thoughts of the inhabitants of a fictional Welsh fishing village, and is planning to make back-to-back English and Welsh language versions of the project, which was previously tuned into a big screen release by filmmaker Andrew Sinclair in 1972.
Allen has cast Notting Hill star Ifans in the role of First Voice, which was originated onscreen by Burton.
Burton's on/off wife Dame Elizabeth Taylor also starred in the 1972 film.
Producers have promised to "veer away from delivering a one dimensional, literal reflection of Thomas' original work" and instead "explore some of the darker, visceral elements" of "a richly funny, filthily fluid dystopian dreamscape - whilst not stooping to mess with Thomas' original text".
Filming on Under Milk Wood is due to begin this summer (14).