A NAZI flag raised on a private property in north-west Victoria is "absolutely disgusting behaviour", Premier Daniel Andrews says.

Cheryl Lawdorn and her partner have been flying the flag over their property in Beulah, just over 200km from Mildura, for several weeks, because of her German ancestry, she told The Age newspaper.

The flag has a black swastika in the middle on a white background, encircled, with imperial German symbols on red backgrounds in each corner.

"The people who are displaying that despicable flag, this is disgusting -- it is absolutely disgusting behaviour," Mr Andrews said on Tuesday.

"If there's any decency in that household, they will take that flag down immediately."

Victorian Parliament is running an inquiry into racial vilification with a focus on recent increased anti-semitic behaviour.