The current density flowing on the closed magnetic surfaces of a tokamak plasma is determined as a function of the externally induced, toroidal electric field and the cross-magnetic-surface density and temperature gradients. It is expressed in terms of a 'pseudo-neoclassical' theory, i.e. a neoclassical theory generalized to include the possibility of anomalous enhancement (uniform in velocity space) of collisions. It is valid in all tokamak regimes ('banana', 'plateau', 'Pfirsch-Schluter' and any combination thereof), for any shape of the (closed) magnetic surfaces and for any plasma composition. The particular case of a clean plasma in which the effect of impurities is taken into account by introducing an effective ion charge for e-i collisions is considered in detail. The influence of an anomalous enhancement of e-e collisions on tokamak reactor scenarios is discussed.