The notion of a { {\rm((}complete-{\rm)} normal{\rm)} vague weak interior ideal} on a {\rm(}{ regular}{\rm)} $\Gamma$-semiring is defined. It is proved that the set of all vague weak interior ideals forms a complete lattice\/. Also, a characterization theorem for a regular $\Gamma$-semiring in terms of vague weak interior ideals is derived. Another interesting consequence of the main result is that the cardinal of a non-constant maximal element in the set of all {\rm(}complete-{\rm)} normal vague weak interior ideals is 2.