Fewer than half of the nation's councils have enough staff trained to respond to marine oil spills - prompting questions over whether authorities are prepared to deal with a major leak.
According to Maritime New Zealand, just 47 per cent of regional councils have trained responders at or above 80 per cent of the recommended number - and some of the biggest shortfalls are in regions where the most oil drilling and exploration take place.
Written responses provided to the Green Party by Transport Minister Simon Bridges showed Canterbury, Gisborne and Taranaki respectively had 63 per cent, 75 per cent and 69 per cent of the recommended number of responders.
The West Coast and the Chatham Islands, each with 50 per cent of the quota, and Northland, at 57 per cent, had lower numbers still.
However, Bridges and Maritime New Zealand say there are enough resources to deal with an oil spill - and capacity is being reviewed.
In line with international practice, New Zealand's spill response system operates in a three-tier system, where "Tier 1" responses are led by industry.
Under legislation and strict requirements, all vessels, oil transfer sites and offshore installations have to provide a marine oil spill contingency plan and prove they have the measures in place to deal with a spill.
But in "Tier 2" situations, where spills are too large for operators to deal with or where no responsible party can be identified, regional councils must step in and each must have their own contingency plans.
In his response to the party, Bridges said the recommended numbers of oil spill responders for each region were set before 2000 - when the combined area subject to exploration and mining permits was 1445sq km, compared with 126,865sq km today.
But Maritime New Zealand had been assessing the recommended numbers and was due to complete this process by the end of the year, he said.
Green Party energy spokesperson Gareth Hughes said the review was "no excuse for not meeting current targets".
"Oil spill preparedness is not something we should be cutting corners on. Why would we put our beaches, our marine life and our fishing industries at risk for a few dollars here and there?"
If smaller regions were struggling to meet requirements, the Government "should be more proactive supporting them because an oil spill affects the whole country", Hughes said.
"The Rena disaster showed us we have to be prepared - catastrophic oil spills can and do happen in New Zealand."
But Bridges said Maritime New Zealand was satisfied regions had enough trained responders to respond to Tier 2 incidents and that the sum total of all regionally trained responders in New Zealand was sufficient to support a Tier 3, or national, response.
The agency also told the Herald the Government was able to provide extra resources and "we have agreements with international partners to augment New Zealand's capability at any time".