A process for making a flame retardant polyurethane foam, the process comprising reacting a PO based polyol with foam-forming reactants to provide said polyurethane foam, wherein said polyol is prepared by ring-opening polymerization of alkylene oxide in the presence of a composite metal cyanide complex catalyst, and wherein said polyol is either free from EO moieties or comprises EO moieties in an amount of at most 1% w/w.