The St\"uckelberg formalism is a field-enlarging transformation

It is shown that the St\"uckelberg formalism can be regarded as a field-enlarging transformation that introduces an additional gauge symmetry to the considered model. The appropriate BRST charge can be defined. The physical state condition, demanding that that a physical state is to be anihilated by the BRST charge, is shown to be equivalent to the St\"uckelberg condition. Several applications of the new approach to the formalism are presented. The comparison with the BFV procedure is given. (The author field has been corrected.)