  Motivated by recent theoretical approaches to high temperature
superconductivity, we study dynamical mass generation in three dimensional
quantum electrodynamics ${\rm QED}_{3}$) in presence of irrelevant four-fermion
quartic terms. The problem is reformulated in terms of the renormalization
group flows of certain four-fermion couplings and charge, and then studied in
the limit of large number of fermion flavors $N$. We find that the critical
number of fermions $N_c$ below which the mass becomes dynamically generated
depends continuously on a weak chiral-symmetry-breaking interaction. One-loop
calculation in our gauge-invariant approach yields $N_{c0} = 6$ in pure ${\rm
QED}_3$. We also find that chiral-symmetry-preserving mass cannot become
dynamically generated in pure ${\rm QED}_{3}$.
