Auckland's ASB tennis Classic has lost one of its drawcards.

Former world number one Victoria Azarenka has withdrawn from the tournament due to personal reasons.

The Belarusian has been facing ongoing custody battles with her former partner and is not allowed to leave California as a result.

Tournament director Karl Budge said it's a real shame.

"It's a really tough one to swallow on Christmas Eve, not the Christmas present we were looking to receive but it's probably a little bit more painful for Vika and I think we all can appreciate it at this time more than most, that family has got to come first."

The women's draw of the ASB Classic begins on New Years Day.