The present invention relates to the novel method for the preparation of a polymer of (meth)acrylic acid in aqueous solution, said polymer having a molecular mass of less than 6,500 g/mol, as measured by SEC, using a compound of copper carbonate type or one of its derivatives and a compound of formula (I): according to which: X represents Na, K or H and R represents an alkyl chain comprising from 1 to 5 carbon atoms.