  We present the simplest possible model for a semi-local string defect in
which a U(1) gauged subgroup of an otherwise global SU(2) is broken to produce
local cosmic strings endowed with current-carrying properties. Restricting
attention to type II vortices for which the non current-carrying state is
unstable, we show that a condensate must form microscopically and
macroscopically evolve towards a chiral configuration. It has been suggested
that such configurations could potentially exist in a stable state, thereby
inducing large cosmological consequences based on equilibrium angular momentum
supported loop configurations (vortons). Here we show that the current itself
induces a macroscopic (longitudinal) instability: we conclude that type II
semi-local cosmic strings cannot form in a cosmological context.
