Having seen how public opinion changed the Government's mind about mining conservation land, the Green Party is hoping its new "save the wild rivers" campaign will have the same result.

Conservation spokesman Kevin Hague says if Meridian Energy is allowed to dam the Mokihinui River it will be destroyed forever.

"We're asking (Prime Minister) John Key's government not to under-estimate public opinion again," he said today.

"New Zealanders love our wild rivers and the flora and fauna that make their homes there - so let's protect them."

Mr Hague said the Government backed down on mining conservation land and had ordered a moratorium on taking more water from the Hurunui River.

"Today I have launched a petition requesting Parliament to protect the Mokihinui and introduce better legislative protection for our remaining wild rivers," he said.

"Their significance for biodiversity, recreation, tourism and ecosystems far outweighs and short-term gains we can make from damming them."

He said the Mokihinui River on the South Island's West Coast had been identified as one of New Zealand's most ecologically valuable wild rivers.

It flows from Kahurangi National Park and passes through a gorge.

Mr Hague said Meridian, a state-owned power company, planned a hydro dam that would drown 330 hectares of rainforest.

"John Key needs to rein in Meridian once and for all," he said.