The Cook Islands MP Norman George says an arrangement dating back to the mid 1980s which meant the country's biggest company paid less import duty has cost the country millions of dollars.
A Cook Islands Audit Office Investigation two years ago found Coca Cola's exclusive agent in the island, the Cook Islands Trading Company, had an arrangement with Customs, which meant it paid less import tax.
Mr George says the government did nothing when the report was tabled in parliament in 2011.
Excerpts have been published in New Zealand magazine Investigate which have been noted in Rarotonga.
The independent MP says the Cook Islands Trading Company enjoyed a huge advantage over other importers who have been left demoralised by the revelations.
"For the biggest company to get away with cheating and then for the government of the day to simply ignore it, that's what hurts the people, that the Puna government refused to do anything about it."
Norman George says the report estimated that the amount lost in import taxes was between 15 - 20 million dollars.
He says there should be a full inquiry.