A Johannesburg schoolboy appealed to education authorities after refusing to answer an exam question on Harry Potter because he believes the best-selling children's books promote witchcraft.

Eighteen-year-old John Smit did not answer a comprehension question on a review of one of JK Rowling's books on the boy wizard, worth 30 percent of his English exam.

"He wouldn't answer it because it supports witchcraft, and we're against witchcraft, the Bible is against witchcraft," Smit's mother, who did not wish to give her first name, said.

The family has written to provincial director of examinations to complain. Authorities have yet to respond.

"I hope they will give him his average mark. This shouldn't happen again," she said.

African Christian Democratic Party MP Cheryllyn Dudley said South Africa needed a clear policy to avoid other pupils facing moral dilemmas during exams.

"I have read Harry Potter books, I have researched them thoroughly, and my personal opinion is that they are witchcraft manuals," Dudley said.