An oil spill the size of Deepwater Horizon is likely to occur again and New Zealand is not ready to respond if it happens here, the Greens say.
The explosion on BP's Deepwater Horizon rig killed 11 crew members and saw 600,000 tonnes of oil spill into the Gulf of Mexico.
It was the worst oil spill in United States history, but a new report suggests it may not be a rare event.
An oil spill of the same scale can be expected every 23 years, a report published by the European Commission said.
''The study suggests that the Deepwater Horizon accident, the largest recorded oil spill, cannot be considered as a particularly rare event.''
Green Party energy spokesman Gareth Hughes said that was scary considering New Zealand's unpreparedness and the Government should abandon its ''reckless'' deep sea drilling programme.
''The Government is simply gambling. The Government knows that we aren't prepared for an oil spill in deep water, they are just hoping it won't happen.''
"We do not have the resources and our remote location meant help was too far away.
''The Government won't even require oil companies to have a relief rig nearby; a relief rig was what eventually stopped the Gulf of Mexico spill after some 86 days.''
But Energy and Resources Minister Simon Bridges said the Government was working to strengthen the rules.
Proposed changes included consideration of a company's track record when awarding permits, new rules around the management of oil wells, and minimising the likelihood of a spill.
The main responsibility was placed on the oil companies themselves, he said.
These obligations included comprehensive environmental assessments, extensive safety case requirements, detailed oil spill contingency planning and the ability to contain and stop the release of oil as soon as possible.
More than 48,200 personnel responded to the Deepwater spill, 127 surveillance aircraft were involved and thousands of ships were used.
By comparison New Zealand has just 400 regional responders, 60 to a high level. Maritime New Zealand conducted a review in 2011 and concluded the industry was doing little preparation.
The focus of a response would likely be ''shoreline-based'' - essentially cleaning up the beaches.
''The unpredictable nature of the sea conditions around New Zealand, which is exposed to the prevailing (south-westerly) winds coupled with low sea temperatures make tackling an offshore oil spill extremely difficult,'' the review said.
We were ready to deal with a spill of about 5500 tonnes - less than 1% of the Deepwater spill.
The Government last year awarded 10 permits for oil exploration; two in the Pegasus Basin off the south Wellington coast, one in the Great South Basin and seven in the Taranaki Basin - including five onshore.