Based on O II recombination lines we present a new calibration (called O II_{RL}) of Pagel's O_{23} indicator to determine the O/H abundance ratio in extragalactic H II regions and emission line galaxies. The O II_{RL} calibration produces O/H abundances about a factor of two higher than those derived from the T(4363) method with t^2 = 0.00. The O II_{RL} calibration has implications for the study of different properties of emission line galaxies such as their metallicity, star formation rate, and initial mass function. The O II_{RL} calibration also affects the abundance determinations based on other O/H indicators, that include collisionally excited lines, like those known as O_3N_2, N_2, S_{23], Ar_3O_3, and S_3O_3. We argue that the controversy between the T(4363) method and the photoionization models method to derive O/H values is mainly due to temperature variations inside the observed H II regions.