The general structure of electromagnetic currents for electrodisintegration of nuclei near threshold, e(-) + A --> e(-) + A(1) + A(2) (A, A(1) and A(2) are arbitrary nuclei or hadrons with spins 0, 1/2 and 1), are established. Considering nuclei as elementary particles with the definite values of spin and space parity and using the conservation of hadronic electromagnetic current and P-invariance of hadron electromagnetic interaction, the spin structure of the amplitudes of the processes gamma* + A --> A(1) + A(2) is derived in terms of threshold electromagnetic form factors. The present formalism is valid for any nuclear structure and any reaction mechanism. The structure functions, which characterize the scattering electrons on the polarized target, are calculated as quadratic combinations of the form factors. These structure functions are used for the analysis of the problem of complete experiment for the full determination of all threshold form factors. P-odd part of electromagnetic current, induced by P-odd nuclear forces, is parametrized also in terms of the corresponding form factors. The processes with the following combinations of spins of hadrons e(-) + 1 --> e(-) + 0 + 0, e(-) + 1 --> e(-) + 1 + 0, e(-) + 1/2 --> e(-) + 1/2 + 1 and e(-) + 1/2 --> e(-) + 1/2 + 1/2, and with different combinations of space parities of nuclei A, A(1) and A(2), are examined within this approach. (C) 1998 Published by Elsevier Science B.V.