We used a generalized Monte Carlo sampling of the canonical ensemble to describe ionic condensation and binding on charged interfaces. This procedure includes all ion-ion, site-site, and ion-site long-range electrostatic correlations. It predicts a noticeable influence of the inter particle separation on the degree of ionization of the colloids. As a consequence, the inner and outer face of two disklike particles are not symmetrically ionized at separations less than 100 Angstrom. Because of the resulting asymmetry of counterions condensation, long-range electrostatic attraction is expected to occur between such ionisable or neutralizable particles, even in the presence of monovalent counterions.