The invention relates to a thermoplastic composition comprising at least one polyester (A) which is an aliphatic polyester; at least one starch (B); at least one organic plasticiser (C) for starch; and at lest one monoester compound (D) of fatty monoacid comprising at least 12 carbon atoms and glycerol. The composition is characterised in that the amount by weight of compound (D) varies between 0.05 and 1.7 parts per 100 parts of the dry weight of the different constituents (A), (B) and (C).