A one-part, multi-phase colour developer concentrate having an aqueous phase and an organic phase, wherein the organic phase is constituted by a carboxylic acid amide or urea derivative which is liquid at room temperature and the concentrate contains at least one compound of the formulae (I), (II) or (III) as antioxidant: in which R1 means alkyl, R2 means alkyl or aryl and n means 0 or 1 and at least one of the residues R1 and R2 contains at least one —OH, —COOH or —SO3H group; in which R3 means an alkyl or acyl group; in which R4 means an alkylene group optionally interrupted by O atoms and m means a number of at least 2, is in particular suitable for the production of a colour developer solution for silver halide materials having an elevated AgCl content.