The outgoing Pacific Chief Trade Advisor is taking issue with a claim many tropical fruits will still be excluded from the Australian and New Zealand markets under the PACER Plus deal.
The trade arrangement among Pacific nations is due to be signed in June after negotiations were completed last week.
Edwini Kessie said the New Zealand Green Party MP Barry Coates was wrong to claim there is a lack of access.
He said the issue was the difficulty Pacific Island countries often have in establishing rigorous bio-security systems, but under the deal New Zealand and Australia were committed to help the smaller nations achieve this.
"So the statement that they don't have access to Australia for tropical fruits is not accurate," Dr Kessie said.
"I mean I think it should be said in the context that they cannot meet their applicable bio-security requirements.
And in PACER Plus Australia and New Zealand have undertaken to assist the countries to meet those standards."
Dr Kessie, who has returned to his position at the WTO in Geneva, said he was confident PACER Plus would bring immense benefits to the island nations.
He said if the island leaders didn't also think this they would not have agreed to the deal.
The two largest Pacific island economies of Fiji and Papua New Guinea were not included in the final negotiations.