Process for the treatment of an exhaust gas polluted by SO x and NO x wherein a flow of said gas is treated with an oxidising reagent in a treatment plant to remove the pollutants from the flow of gas, said process comprising the following fundamental steps: (i). Preparing the oxidising reagent in a mixing unit M-1 fed by an aliquot of water L 01 at the inlet and by an aqueous stream of recirculation reagent L 01-3, the aliquot of water L 01 deriving from splitting water L 0 at the inlet to the plant into two aliquots, first aliquot L 01 and second aliquot L 02 of water, the recirculation reagent L 01-3 being an aliquot deriving from splitting the treatment liquid L 01-2 exiting a first treatment unit S-1, containing sulphates and nitrates deriving from the previous absorption of SO x and NO x in said first unit S-1, the oxidising reagent so prepared being withdrawn from the mixing unit as a stream of oxidising reagent L 01-1 which is sent to said first treatment unit S-1; (ii). Splitting the flow of gas entering the plant G 0 into a first aliquot of gas G 01 and a second aliquot of gas G 02 and sending said first aliquot of gas G 01 to the first treatment unit S-1 and said second aliquot of gas G 02 to a second treatment unit S-2; (iii). Bringing the first aliquot of gas G 01 into contact with the aqueous stream of oxidising reagent L 01-1, withdrawn from the mixing unit M-1 and which feeds the first treatment unit S-1 at the inlet; (iv). Withdrawing at the outlet from the first treatment unit S-1 the treated gas G 04 and the treatment liquid L 01-2, polluted with the pollutants SO x and NO x following the contact with the treated exhaust gas, (v). Splitting the treatment liquid L 01-2 into a first aliquot or recirculation reagent L 01-3 which is recirculated by sending it to the mixing unit M-1 and into a second aliquot or purge stream L 01-4 which is sent to a second treatment unit S-2 to treat the second aliquot of gas G 02; (vi). Withdrawing, at the outlet from the second treatment unit S-2, the treatment liquid L 01-5 which contains sulphates and nitrates deriving from the absorption of the pollutants SO x and NO x during the contact between the purge stream L 01-4 and the gas G 03 which is sent to the first unit S-1 together with the first aliquot of gas G 01. (i). Preparing the oxidising reagent in a mixing unit M-1 fed by an aliquot of water L 01 at the inlet and by an aqueous stream of recirculation reagent L 01-3, the aliquot of water L 01 deriving from splitting water L 0 at the inlet to the plant into two aliquots, first aliquot L 01 and second aliquot L 02 of water, the recirculation reagent L 01-3 being an aliquot deriving from splitting the treatment liquid L 01-2 exiting a first treatment unit S-1, containing sulphates and nitrates deriving from the previous absorption of SO x and NO x in said first unit S-1, the oxidising reagent so prepared being withdrawn from the mixing unit as a stream of oxidising reagent L 01-1 which is sent to said first treatment unit S-1; (ii). Splitting the flow of gas entering the plant G 0 into a first aliquot of gas G 01 and a second aliquot of gas G 02 and sending said first aliquot of gas G 01 to the first treatment unit S-1 and said second aliquot of gas G 02 to a second treatment unit S-2; (iii). Bringing the first aliquot of gas G 01 into contact with the aqueous stream of oxidising reagent L 01-1, withdrawn from the mixing unit M-1 and which feeds the first treatment unit S-1 at the inlet; (iv). Withdrawing at the outlet from the first treatment unit S-1 the treated gas G 04 and the treatment liquid L 01-2, polluted with the pollutants SO x and NO x following the contact with the treated exhaust gas, (v). Splitting the treatment liquid L 01-2 into a first aliquot or recirculation reagent L 01-3 which is recirculated by sending it to the mixing unit M-1 and into a second aliquot or purge stream L 01-4 which is sent to a second treatment unit S-2 to treat the second aliquot of gas G 02; (vi). Withdrawing, at the outlet from the second treatment unit S-2, the treatment liquid L 01-5 which contains sulphates and nitrates deriving from the absorption of the pollutants SO x and NO x during the contact between the purge stream L 01-4 and the gas G 03 which is sent to the first unit S-1 together with the first aliquot of gas G 01.