  The pair production cross section for scalar and vector leptoquarks at $ep$
colliders is calculated for the case of photon--gluon fusion. In a model
independent analysis we consider the most general $C$ and $P$ conserving
couplings of gluons and photons to both scalar and vector leptoquarks described
by an effective low--energy Lagangian which obeys $U(1)_{em} \times SU(3)_c$
invariance. Numerical predictions are given for the kinematical regime at HERA
and LEP~$\otimes$~LHC.
