The purchase of the Audi was signed off by Tania Pene, the Tamakis' closest adviser.
Independent charity researcher Michael Gousmett said: "That's not what charity is about. These organisations are here to provide public benefit and, if you've got members of this organisation running around in super-expensive vehicles, you've got to ask the question to what extent are they providing public benefit rather than looking after their own self-interests?"
He said it had become common for a charity to also be listed as a limited liability company. "I wonder how much this is being taken advantage of in the charity sector."
In June, Hannah Tamaki took out a personal loan against an E350 CDI Mercedes Benz - which retails for $99,000 new - and held on to the PROT0N number plate.
Te Hahi o Nga Matamua Holdings' last annual return filed with the Charities Service was for the year ending March 30, 2012. It was one of 14 Destiny-affiliated charities that are late in filing annual returns. Destiny Church spokeswoman Anne Williamson did not return a request for comment.
The Charities Service told the Herald on Sunday last week it had sent late notices about the overdue filing of the 14 charities.