It is proved that in any order of perturbation expansion the dimensionally regularized Feynman integration may be multiplied by an arbitrary analytic function of the space-time dimension, which can be absorbed in the redefinition of the bare coupling constants so that the finite renormalized quantities are unchanged. It is also shown that the Ward-Takahashi identities of a gauge theory are unaffected by this multiplication factor. A most convenient choice of the multiplicative analytic function is suggested and the effective potential of massless $\ensuremath{\lambda}{\ensuremath{\varphi}}^{4}$ theory is calculated in the two-loop approximation as an explicit example.