Illegible handwriting is being blamed for nearly 7,000 identity documents found to have incorrect information every year.
Figures released under the Official Information Act show 17,852 births, deaths and marriage certificates, more than 1,000 passports and hundreds of citizenship certificates were found to have incorrect details over a three-year period.
Department of Internal Affairs spokeswoman Jo Watt said the flaws were mainly caused by poor writing. "For the most part the departmental errors result from misspellings of names and other information, particularly where the department is interpreting handwritten applications."
Out of the flawed certificates, 1,326 incorrect ones were sent out before Internal Affairs staff picked up the mistakes. Among passport errors, common mistakes were passports being issued in the incorrect sex (187), the wrong name (141), and the wrong image being used (85).
Labour Party spokesman Trevor Mallard said errors should be taken seriously.
"These documents are really important. The security of our country depends on them."
Danny Toreson, of Thompson and Toreson Investigations, said nearly 20,000 incorrect [identity documents] was "pretty significant, particularly if they have incorrect names that can be used to gain more documentation".
This week it was revealed an accused sex offender from the West Coast was able to flee to Australia because a Ministry of Justice employee ticked the wrong box on a form. The Christchurch man, 42, was facing charges of sexually abusing his daughter.
• 1,006 flawed passports
• 187 wrong sex
• 85 wrong picture