In the past five years, 5057 foreign nationals were refused entry at the border - 3262 were believed to have non-genuine reasons for travelling and 448 were seen as "likely to commit a crime in New Zealand".
However, an Immigration NZ spokesman said yesterday there was no breakdown of how many were travelling on South African passports.
Britain also stopped allowing South African passport holders to enter without a visa three years ago, saying South Africa "fell short of the required standard" of passport security.
Anneli Botha, senior terrorism researcher at the International Crime in Africa Programme, says South Africans can use their driver's licence, identity book or a birth certificate to apply for a passport, and fake South African birth certificates can be bought easily on the black market.
In an article for the Institute for Security Studies, she lists a number of al-Qaeda-linked terrorists caught with South African passports, including two alleged to be part of a 2006 plot to blow up airliners.