RADIO NEW ZEALAND INTERNATIONAL
Dr Inoni Betuela from the Institute of Medical Research said over 80% of drugs are sourced from uncertified companies.
He said more than half of the content of the sampled tablets of primaquine was made up of sugar and inactive ingredients.
He says while primaquine is not that widely used, other common drugs like quinine and amoxicillin also had significant levels of failure.
The team sampled 360 samples, of seven different anti-malarial and antibiotic drugs.
Dr Betsuela says the result is a clear warning to the health department, and there needs to be more scrutiny of the sources of medicines.
"We should be using companies or factories that are WHO certified, to say that they comply to the good manufacturing practice and say that most of the drugs they're producing are of good quality," he said.