  The finite temperature effective potential in the 2+1 dimensional
Nambu-Jona-Lasinio model is constructed up to the next to leading order in the
large $N$ expansion, where $N$ is the number of flavors in the model. The
distinctive feature of the analysis is an inclusion of an additional scalar
field, which allows us to circumvent the well known, and otherwise unavoidable
problem with the imaginary contribution to the effective potential. In
accordance with the Mermin-Wagner-Coleman theorem, applied to the dimensionally
reduced subsystem of the zero Matsubara modes of the composite boson fields,
the finite temperature effective potential reveals a global minimum at the zero
of the composite order parameter. This allows us to conclude that the
continuous global symmetry of the NJL model is not broken for any arbitrarily
small, finite temperature.
