Seascape Apartments on Customs Street, at 52 storeys and 187 metres high, is being built by a Chinese contractor, using structural steel manufactured in China.
New Zealand's strict seismic steel standards make welding beams and frames difficult.
Australasian Certification Authority for Reinforcing and Structural Steels (ACRS) executive director Philip Sanders said problems with tainted steel supply worldwide meant his organisation was not coy about asking questions about the steel supply for the Auckland project.
It was crucial to ensure testing at every stage - of the product, the manufacturing processes, and how it was supplied.
"It really needs to be [an] independent party that sets the test plan ... for international best practice it should not be under the auspices or control of the [steel] supplier."