Bluestone was granted permission at a meeting in January

The Council for National Parks (CNP) is challenging a decision to grant planning permission for Bluestone.

Part of the development falls within Pembrokeshire Coast National Park Authority land but members backed it against the advice of their officers.

The hearing in Swansea is scheduled for three days but the judge may not issue a decision for several weeks.

We will be urging the judge to uphold our concerns and quash this planning permission Ruth Chambers, CNP

The court is expected to hear legal submissions from the CNP, the park authority, and developers.

The CNP, which acts as a watchdog for the UK's national parks, claims authority members went against their own national and local policies in granting permission for the scheme near Narberth that includes 340 timber lodges.

Head of policy Ruth Chambers said: "We have taken the unprecedented step of going to court because of the scale of the Bluestone development.

"It is completely inappropriate in a national park. We will be urging the judge to uphold our concerns and quash this planning permission for what would in effect be a new town in beautiful, unspoilt countryside."

The developers of Bluestone say the project will create 600 full and part-time jobs with a further 200 jobs for contractors and suppliers.

They and the Pembrokeshire Coast National Park Authority will tell the hearing that the plans were given unanimous backing by members after several hearings and prolonged talks.

They will also claim Bluestone is not a planning or environmental precedent as two other major UK holiday villages are built in areas of outstanding natural beauty.

The court will also hear that a landscape and planting programme will ensure the holiday site will not be visible from any existing settlement or private house, and will help improve habitats for wildlife and increase biodiversity.