A mining company has lodged consents to expand its gold and silver mining operations, including under conservation land in Waikato, but an environmental group is pledging court action.

On Tuesday afternoon, OceanaGold Waihi announced it has given its application for its Waihi North Project to Hauraki District and Waikato Regional councils.

It wants to set up an underground mine north of Waihi beneath Wharekirauponga, which is a forest park administered by the Department of Conservation.

OceanaGold says access to the proposed facility will be from an underground tunnel off private land, with no mining at surface level.

It says a tunnel will also allow material to be removed from the site, removing the need for it to be trucked out using public roads.

The facility is part of wider plan to dig a new open pit mine west of its current processing plant, build a new tailings storage facility for mining waste, and create a new rock storage facility.

It says the proposed projects could create several hundred additional jobs in the region and produce billions of dollars of exports over the coming years.

OceanaGold says the consent process will take some time, and that environmental assessments and full technical reports in support of the application would be made publicly available.

'We are determined to stop these mining applications'

Coromandel Watchdog of Hauraki chairperson Catherine Delahunty says it will take its fight to the Environment Court to stop the Wharekirauponga mine.

"We are determined to stop these mining applications on behalf of everyone who loves the forest, including all the life forms who deserve better."

The government should have stopped activity like this when it announced a ban on new mining activity on conservation lands in 2017, Delahunty says.

Tunnelling would require fossil fuels and huge amounts of concrete, which has a heavy climate impact, and was the last thing the country needed, she says.

"We need to be looking after forests not draining their waters and industrialising recreational areas."

-RNZ/Hamish Cardwell.