Disclosed is a method for the preparation of a polyester, which method comprises in a first step, reacting a dicarboxylic acid or a C1-C4 dicarboxylic diester with a diol at a suitable temperature and pressure to effect esterification or transesterification to prepare a precondensate and in a second step, reacting the precondensate to effect polycondensation at a suitable temperature and pressure to prepare a high molecular weight polyester, where a metal phosphonic acid complex compound of the formula is employed in the first step, in the second step or in both the first and second steps as a reaction catalyst.