The present invention relates to a process for dyeing keratin fibres in particular human keratin fibres such as the hair in which said fibres are treated using one or more cosmetic compositions comprising a) one or more dye(s) b) one or more titanium salts and b1) optionally at least one carboxylic acid and c) one or more anionic thickening polymers derived from the polymerization of at least one monomer bearing an organic monoacid function and d) optionally one or more chemical oxidizing agents such as hydrogen peroxide or one or more hydrogen peroxide generating systems.