The Government has deliberately withheld information of "vital national importance" surrounding plans to drill for oil off the Kaikoura coast, Labour says.

Documents showed Environment Minister Amy Adams had kept secret the real risk of an incident occurring at the depths of Anadarko's proposed Kaikoura drilling site, Labour leader David Cunliffe said.

The documents, released by Cunliffe in Christchurch this afternoon, showed Adams had received international research 13 months ago.

It showed a 70 per cent probability of a "reportable incident" happening within a year at the 1500-metre depth of the Kaikoura well. Such incidents could include an oil spill, fire or collision.

The documents showed that while existing shallow-water sites such as Taranaki carried a risk of only about 10 per cent, the risk increased dramatically at deeper levels, Cunliffe said.

"Amy Adams went to great lengths to keep this information from the public. In fact, she told Parliament there is a 'very low risk' of a large-scale oil spill occurring.

"The Government needs to be honest about the risks of deep-sea oil drilling, especially when the Kaikoura community and the wider public hold serious reservations about Anadarko's plans."

Adams said "reportable incidents" covered a wide range of scenarios, including any damage to property, days off work and shut downs, so the 70 per cent figure did not reflect the danger of a spill.



"It's quite wrong to say that that reflects the risk of oil spill," Adams said.

"The risk [of a spill] exists; we've never hidden that fact, but it is a very low risk and the focus needs to be on containing and controlling and stopping them happening, and not just looking at what would happen if they did."

It was not the first time the Government had misled the public over this issue, Cunliffe said.

"Last year the energy and resources minister told Kaikoura residents they would be consulted on exploration drilling but this year National rushed through legislation taking away that democratic right.

"In September Amy Adams said the impact of an oil spill would be 'significant' but it turns out she'd been told it would be 'catastrophic'.

"Last month John Key claimed there had only been one 'problem' in the Gulf of Mexico but there have been 74 major spills."

Head of the Petroleum Exploration and Production Association (Pepanz), David Robinson, said it was vital that Kiwis had responsible information about deep sea oil drilling, but criticised Labour's release of the documents.

"Communities are calling for more responsible information about deep sea drilling. Instead, Labour Leader David Cunliffe's announcement today is riddled with inaccurate assertions which are harmful to the oil and gas industry here in New Zealand and potential investors looking to come to our shores," Robinson said.

"Labour claims they have 'unearthed' secret documents hidden by the Government - the truth is you can find the report online here. Or use Google.

"They claim there is a "well /drilling site" in Kaikoura - again, this is incorrect. Anadarko has planned seismic surveys for the area - but that's as far as it goes.

"Taking information out of context or using images without the commentary and research it was published with is misleading and does not contribute to a balanced conversation that our country needs to have about energy."

Labour's assertion that the probability of an incident increased the deeper you drill offshore was actually based on a report that said it was the number of incidents such as injuries, falls or spills that increased.

"The 70 per cent does not refer simply the probability of a large oil spill - in fact it is saying the more people and machinery you use - the more chance there is of a cut finger, injury, fire or any other incident that you would see on a construction site anywhere.

"We know we still have a lot of work to do to provide Kiwis with responsible information to give them confidence that we operate safely, to the highest standards under robust regulations."

Cunliffe said Labour supported deep-sea mining "in principle", but it wanted all the facts released so people had all the information available. For any consent to be approved under his government, Cunliffe said it would need world-class environmental standards, cleanup capability, full liability cover and a good level of consultation with affected communities.

"A major oil spill would affect our international reputation, not just our environment, and harm our exports and tourist operators. We can't afford to risk our future for a short-term gain," he said.

Cunliffe said the information was of "vital national importance".

"We think it is reprehensible the Key Government has withheld from the New Zealand public for over a year."

Labour had fought to get the information released.

The industry knew it has to earn the social right to explore New Zealand but that balance had been lost under the Key government's approach which he said "time after time, favours the interests of the big end of town".

"I think this is a deliberate attempt by a relevant minister to deny the public information which is absolutely crucial to a mature debate on this issue."

Pepanz welcomed Labour's qualified support for the industry.

"With the world class standards our industry operates under, the real commitment we have to engaging with communities, the first class technologies to not only prevent incidents but to respond and our willingness to take responsibility for our operations should give Labour the confidence that their support of our industry is not misplaced," Robinson said.