Labour said Mr Lines had "descended into the gutter".
Mrs Stuart, a law lecturer formerly known as Gisela Gschaider, is standing as candidate for Edgbaston. She has lived in Britain for 20 years and represented her adopted country in fencing in the past.
Mr Lines, whose ward forms part of the constituency Mrs Stuart is contesting, said: "She's a German wrapping herself in the Union Jack and it's a damned cheek. She's trying to mislead people."
Mrs Stuart said: "People don't care about my place of birth but about what I can do for them and what a Labour government can do for them." She took her husband's name after students had problems spelling her surname. "I want to debate issues," she said, "not individual personalities."Reuse content