The minehead will be built close to the Coast to Coast Walk route

Campaigners opposed to proposals for a giant mine in a national park said they will not mount a legal challenge to planners’ decision.

The Campaign for National Parks has taken legal advice on its options following the North York Moors authority’s go-ahead for the York Potash plans.

It said it will now concentrate its efforts on trying to ensure no similar developments are allowed in the future.

The charity said its decision follows a detailed review of all relevant documentation.

Fiona Howie, Campaign for National Parks chief executive, said: “We remain hugely disappointed that this development was given approval and are convinced that development of this type and scale is not appropriate in a national park.

“However, the only option available to us was judicial review. This would have been focused on challenging the process that has been undertaken, rather than the decision itself. The legal advice we received makes it clear that the national park authority followed the process effectively.

“Having made this decision we will now focus our efforts on making sure this type of major development cannot be approved in national parks in the future.

“These landscapes are meant to be given the highest level of protection by our planning system. But this case makes it clear that these protections are simply not strong enough.”

York Potash wants to build a mine to extract billions of tonnes of polyhalite and other minerals used in fertilisers, much of which it plans to export. The main development will be in the North of the national park, close to the route of the Coast to Coast Walk, and will link to a 36.5km (23-mile) tunnel to Teesside to transport the minerals.

The application was the biggest ever received by a UK national park.