The invention relates to a three-compartment electrolytic cell for production of oxidising disinfectant solutions. The intermediate compartment (300) of the cell is separated from the anodic compartment (200) by a fibrous diaphragm (321) in intimate contact with an anion-exchange membrane (320). The diaphragm (321) is formed by a network of organic polymer fibres mechanically bound to ceramic particles. The cathodic compartment (400) is separated from the intermediate compartment (300) by a cation-exchange membrane (340). Within intermediate compartment (300) a saturated solution of sodium chloride (510) is recycled. Inside tank (500) a decomposition catalyst is contained.