The Government is permitting petrol and mining exploration in marine mammal sanctuaries – home to rare dolphins, whales and seals.

Six sanctuaries around New Zealand's coastline are meant to provide a permanent refuge for marine mammals in fisheries waters.

But Green Party MP Gareth Hughes has branded them "sham sanctuaries" as oil companies have been granted 10 permits in four of the protected areas.

He said the exploration would threaten rare sea creatures such as the endangered maui's and hector's dolphin, as well as sea lions, fur seals and southern right whales.

"What we are seeing is a sham protection.

"Mineral exploitation will be able to happen where we are supposed to be protecting threatened animals."

He said there was "legitimate concern" about seismic surveys where airguns were used to produce powerful underwater sounds.

The Government says it will regulate seismic testing by placing observers on surveying ships and is reviewing a 2006 code of practice.

An Otago University marine scientist, associate professor Steve Dawson, said the low frequency pulses were "extremely loud" and could cause deafness or "the bends" in animals that came too close.

"These air guns are the loudest source that is possible to use without using explosives.

"The trouble with that is we really don't know much about how they affect hector's and maui's dolphins. But you'd have to argue that it's not likely to be good.

"You would have thought that it would have been a good idea in those very sensitive areas to be a little bit more precautionary."

In April, Forest & Bird called for most seismic testing off Taranaki to be halted to save maui's dolphins. It pointed to a mass stranding of dolphins in Peru as evidence that deep water sonar could be harmful.

The animals had damage to their middle-ear bones, a sign of "the bends".

Forest & Bird noted that the Bureau of Ocean Energy Management halted deep-penetrating seismic surveys after sick and dead calf bottlenose dolphins washed up in New Orleans.

But Petroleum Exploration and Production Association chief executive David Robinson said the industry had been co-existing with marine mammals for decades.

"There is no evidence of adverse impacts from seismic surveying on marine mammals.

"Nevertheless the industry is always looking to improve and wants to ensure all steps are taken to minimise potential impacts on marine mammals without unduly affecting normal operations."

Conservation Minister Kate Wilkinson said activities such as seismic surveying could be restricted to minimise harm to marine mammals.

"The sanctuaries were originally created as a result of the maui's and hector's dolphins Threat Management Plan.

We have brought forward the review of this plan to make sure we are doing all we can to protect these rare treasures."

Ms Wilkinson said there were no current instances of mining in an MMS.