The decision represents a startling "David and Goliath'' victory for the conservation groups who fought to preserve the landscape in a remote part of Central Otago.

Consents for the project were declined in a mammoth 350-page ruling by the Court, published today.

Save Central co-ordinator Graye Shatkey said environmentalists had won a "comprehensive victory'' in the battle against Meridian Energy's Project Hayes application.

The court's ruling declined consents, originally granted by Central Otago District Council and Otago Regional Council, for the farm - on the remote Lammermoor Range.

The farm would have been the largest in the southern hemisphere.

Save Central was set up to co-ordinate the appeal by appellants from the Manitototo Environmental Society and the Central Otago Environmental Society.

Mr Shattky said the decision was a comprehensive victory for the appellants.

Morrison Kent lawyer Ian Gordon, for the appellants, said the legal team was thrilled by the decision.

"It was real David and Goliath stuff. The court has found that Meridian did not provide the evidence they needed and there was no cost-benefit analysis,'' he said.

He said the decision had noted the Government's "remarkable'' support for a project that presented a case without proper analysis.

Meridian Energy are expected to release a statement later today.