[en] In this paper, we present methodology for investigating theoretically parity violation in both the elastic and break-up channels of electron--deuteron scattering, restricting ourselves to energies in which non-relativistic expansions are allowed for nucleons. The deficiency in the standard impulse approximation related to gauge invariance is remedied by relating it to the ''elementary particle'' treatment. Results for parity violation in elastic electron--deuteron scattering are presented and discussed