A multimillion-pound holiday village in west Wales will be at the centre of a legal battle, it has been confirmed.
Opponents claim the development would set a precedent in the park
The body which acts as a watchdog for national parks has announced it will take the Pembrokeshire Coast National Park Authority to the High Court over its backing for the Bluestone project.
The Council for National Parks (CNP) said it took the "exceptional" decision with a "heavy heart" over a scheme it claims would be harmful.
But the developer of the 500-acre leisure and sports village, which would create 600 permanent jobs, criticised its "predictable delaying tactic".
Part of the village is on land belonging to the national park, which had to give its approval before it could go ahead.
The park authority gave unanimous backing last month.
After the decision the CNP called for the Welsh Assembly Government to intervene, and had already warned that it was considering legal action.
Ruth Chambers, head of policy at the CNP, said: "We have taken the exceptional step of challenging the national park authority's decision in the High Court because of serious legal concerns about the authority's disregard for its own policies and the way in which the decision was made".
She said the CNP had done all it could to avoid a legal challenge as it should always be a last resort.
"However given the major issues at stake for the future of national parks we have decided to take that last resort and have instructed our lawyers to issue legal proceedings immediately," said Ms Chambers.
"We take this decision with a very heavy heart. CNP is a staunch supporter of the work of the national park authorities.
"However in the case of Bluestone we think that the park authority's judgement is seriously flawed and are prepared to challenge this in court".
The £60m park would include 340 log cabins, a snow dome and a sports club.
Bluestone chief executive William McNamara said he had expected the legal action.
He said the park authority had been advised that all correct procedures were followed strictly and there had been such a long planning process to ensure it was not open to legal challenge.
He told BBC Radio Wales: "We're not surprised at what they are doing. They've tried all these 11th hour tactics since day one. They've been very unhelpful. "
He said it would affect two cornfields, not overlooked by any homes and it was not part of the coastal national park.
"This is serious because if they were succesful, we're talking 600 full-time year- round jobs in Pembrokeshire and we find it very tiresome at this stage.
"The reality is this proposal has been democratically voted in. What they are challenging is that they don't like the decision."