A view near Whitby, northeast England close to the proposed site for a potash mine beneath one of Britain's national parks

A plan to build a huge potash mine beneath one of Britain's national parks was approved on Tuesday, despite stiff opposition.

Mining firm Sirius Minerals is to dig a 1,500 metre fertiliser mine below the rolling woods and grasslands of the North York Moors National Park in a 1.7 billion ($2.7 billion, 2.4 billion euros) investment.

The York Potash project was opposed by a consortium of 29 campaign groups, including the Campaign to Protect Rural England, which said that the mine was a "huge threat" to the moors and undermined the protection of all national parks.

Members of the North York Moors National Park's planning committee granted permission in a special meeting in Sneaton Castle in the north York town of Whitby, where hundreds had gathered to hear the result.

It was approved by eight votes to seven after hours of discussion, with the result cheered by supporters.

"We're obviously very happy but the hard work only begins now," said Sirius Minerals chief executive Chris Fraser, adding that the mine would bolster government efforts to strengthen the economy of northern England, which lags behind the south.

"We'll go and celebrate but then we'll get on with the real job of building a mine."

Sirius Minerals says it will minimise impact by hiding the mine infrastructure underground and concealing it in agricultural style buildings.

"We believe the benefits far outweigh the impact and we're doing everything we can to mitigate it," Fraser said.

Three local members of parliament had written an open letter to the planning committee backing the scheme, calling it a "lifetime opportunity to improve the lives of thousands of people in our area".

But campaigners had countered that there was no evidence of a national need for the development, that alternative sites had not been fully considered, and that harm to the was inevitable.

The chief executive of the North York Moors National Park Authority, Andy Wilson, said it was the largest planning application ever considered by an English national park.

"I appreciate that there will be many disappointed by today's decision but members felt that the long term benefits for the local, regional and national economy were transformational," Wilson said.

The Campaign for National Parks called for a public inquiry following the decision.

"We have long maintained that this project is completely incompatible with national park purposes," said campaigns manager Ruth Bradshaw.

"The promised economic benefits could never justify the huge damage that it would do to the area's landscape and wildlife and to the local tourism economy."

The mine will extend 1,500 metres below the park, before tunnelling outwards.

The mined polyhalite is planned to be pumped underground 48 kilometres north to the coastal area of Teesside for processing and shipping.