  Using the collective variables theory, we study the effect of competition
between Coulomb and dispersion forces on the gas-liquid phase behaviour of a
model ionic fluid, i.e. a charge-asymmetric primitive model with additional
short-range attractive interactions. Both the critical parameters and the
coexistence envelope are calculated in a one-loop approximation as a function
of the parameter $\alpha$ measuring the relative strength of the Coulomb to
short-range interactions. We found the very narrow region of $\alpha$ bounded
from the both sides by tricritical points which separates the models with
"nonionic" and "Coulombic" phase behaviour. This is at variance with the result
of available computer simulations where no tricritical point is found for the
finely-discretized lattice version of the model.
