A Taranaki environmental group wants an investigation launched into the crack that was found at the offshore Maari oil platform, 80 kilometres off the southern Taranaki coast.

A 1.4 metre crack was found four metres below the waterline - a discovery serious enough to force operators OMV to stop work and clear the platform.

OMV believes the crack was caused by the constant pressure of waves and the wind.

But Catherine Cheung, spokesperson for pressure group Climate Justice Taranaki, thinks a further investigation is warranted, "which looks at the other ageing infrastructure in Taranaki because many of these installations are very old - twenty, thirty, forty years old."

Labour Leader Andrew Little said earlier this week that some of the offshore facilities have been there for nearly half a century, and it was worrying that some of them are beginning to show signs of wear and tear.

"It might be a bit of a wake-up call for rest of that industry to make sure that they're checking those structures and those assets, whether they're onshore or offshore, to ensure that they're sound," he said.

OMV New Zealand is one of the country's largest liquid hydrocarbon producers, the third largest gas producer, and a major explorer in a number of offshore basins around New Zealand, particularly the Taranaki Basin.