  In thermal field theory selfconsistent (Phi-derivable) approximations are
used to improve (resum) propagators at the level of two-particle irreducible
diagrams. At the same time vertices are treated at the bare level. Therefore
such approximations typically violate the Ward identities connected to internal
symmetries. Examples are presented how such violations can be tamed by a proper
choice of representation for the fields which describe the system under
consideration. These examples cover the issue of massless Goldstone bosons in
the linear sigma model and the Nambu--Jona-Lasinio model and the problem of
current conservation in theories with massive vector mesons.
