A cost-effective process is described for the preparation of a stable and non-hazardous brominating reagent containing 2:1 stoichiometric ratio of alkali bromide to alkali bromate. The process comprises of reacting alkaline bromine intermediate mixture, obtained from bromine recovery plant, with chlorine gas in the presence of a strong alkali to oxidize the bromide ions to bromate ions. This brominating reagent is useful for the bromination of aromatic compounds by substitutions.