The Ministry for Primary Industries will not ban Australian fruit despite an explosion of Queensland fruit flies in Australia in recent months.
A link between Australia and fruit flies found in Whangerei this year had not been established, according the ministry. A male Queensland fruit fly was detected in Whangerei in January, and another was discovered on 1 April.
The insect is considered one of the biggest threats to the country's horticulture industry.
The Labour Party believes fruit imports from Australia should be suspended until the fruit fly pathway is identified and closed.
But a Ministry for Primary Industries deputy director Andrew Coleman said it was not known how the Queensland fruit fly got into the country so banning Australian fruit may not solve the problem.
"At the moment with the work we're doing around the pathways that fruit fly may come into New Zealand, we don't have a lot of certainty around what that pathway is.
"It's a very complicated area when you think about the likelihood that a fruit fly has come here in an egg and larvae state and it's likely to be on fruit and vegetables.
"That's a very fine state, an egg or larvae, something only ever picked up on a microscope - so it's a very difficult thing to have conclusive proof that it came in on this particular fruit from this particular area of Australia."